The present invention relates generally to methods for patterned depositions of a material onto a substrate and, more particularly, to methods for selectively depositing a conductor onto specified regions of a polymeric substrate.
Polymeric materials, in general, and fluoropolymers, specifically, have received increased interest in the electronics industry due to their attractive properties including: low dielectric constant, low dissipation factors, high thermal stability and high chemical resistance. However, the chemical and physical inertness of fluoropolymers, such as poly(tetrafluoroethylene) (PTFE), makes it difficult to deposit any material thereon. For this reason, copper films on PTFE are generally formed by mechanical rolling processes. With such a process it is difficult to produce narrow sub-micron sized line patterns. In addition, this technique disadvantageously can require a plurality of steps. Consequently, considerable interest has focused on alternative methods of depositing thin metal films on PTFE, e.g. ion plating, presputtering, plasma enhanced vapor deposition and heavy ion irradiation. More recently, Prohaska et al in U.S. Pat. No. 4,933,060 describe a method for preparing a fluoropolymeric substrate surface for deposition of a thin metal film thereon by etching a surface thereof with a reactive gas plasma process. Alternatively, Martinez et al in U.S. Pat. No. 5,066,565 describe a method of preparing a surface of a fluoropolymeric substrate for deposition of a thin metal film thereon by selectively irradiating the surface with an ionizing radiation source and then etching it to produce regions of the surface which have enhanced adhesion characteristics. The present invention provides novel methods which greatly enhance the ability to efficiently produce patterned depositions on a polymeric substrate having micron sized dimensions as shall be more fully described.